Hioki DSM-8542, Instruction Manual, Page: 111 / 140

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(9) RDT? command (Most recent data read)
This command is mainly used in reading measured data during measurement in
the Internal Trigger mode. No need to use this command in the other trigger
modes or in the sequential measurement mode.
(10) *STB? command (Status byte register read)
This command is a query command and cannot be used in detection of
measurement end and other states.
For example, sending the *STB? command after sending the MTG command will
overwrite results of measurement performed by the MTG command with response
data in answer to the next *STB? command, disabling readout of measured values.
(11) *OPC command (OPC bit setting after completing all processing)
Use this command to detect completion of processing of a command that does not
have response data.
For example, when executing the *SAV command, SRQ can be generated upon
the completion of saving by executing “*SAV 1;*OPC” after resetting the mask of
the OPC bit of the Standard Event Status register by “*ESE 1” and after resetting
the mask of the ESB bit of the Status Byte register by “*SRE32.”.
The OPC bit is not cleared automatically and the registers must be cleared by
issuing the *CLS command.
(12) Detecting end of command with response data
Query commands and trigger commands have response data and detection of end
of processing of them can most suitably be accomplished by monitoring the MAV
bit of the Status Byte register.
The MAV bit remains set as long as output data exists in the output queue. By
resetting the mask by “*SRE 16,” SRQ can be generated when the MAV bit is set
first.
The MEC bit can be used in detection of end of detection only in the Manual
Trigger, External Trigger and Sequential Measurement modes. However, the
mask should be canceled by “*SRE 1” and monitoring by SRQ is required. The
MEC bit indicates “during measurement” or “ “during shutdown” and end of
measurement cannot be detected merely by reading the status byte by polling.
SRQ is generated by the MEC bit at the variation point of the MEC bit when
measurement is completed so that detection by SRQ will be possible.
(13) End detection of command without response data
In case of a command without response data, detect it by the *OPC command
mentioned in 11).
(14) Read of response to query (Output queue readout)
Several query command or trigger commands can be set by continually sending in
the following formats. Response data of each command enters the output queue
in the order of command execution.
Read response data as follows:
Example 1: When reading whole data of the mask register.
Send “DSE ; *SRE? ; *ESE?” Then read the data three times or
repeat data reading till the MAV bit is cleared.